Bacterial Communities Associated with Tufa Deposits and Characterization of Indigenous Calcifying Bacterial Isolates from Jiuzhaigou National Nature Reserve, Sichuan, China

Abstract

Tufa is a common calcium carbonate deposit in karst landscapes and microbes may play an important role in its formation. As an important natural resource treasure trove, the diversity of bacteria from the Jiuzhaigou National Nature Reserve tufa deposits and their potential to deposit carbonates are still unknown. In this study, 16S rRNA gene sequencing technology was used to assess the bacterial community composition of Pearl Shoal in Jiuzhaigou National Nature Reserve. The results showed that the main dominant phyla were Proteobacteria, Cyanobacteria, Bacteroidetes and Actinobacteria. With the gradual increase of flow rate, the bacterial community structure was gradually simplified and the dominant phylum changed. The community structure of different sampling sites was significantly different. Besides, 17 strains capable of precipitating calcium carbonate were isolated using microbiological methods. The two strains with relatively strong calcium-forming properties were identified as Leucobacter sp. (J1) and Brucella sp. (J2), respectively. Both strains were able to elevate the environmental pH and produce extracellular polymeric substance (EPS). However, Leucobacter sp. (J1) formed calcite crystals with spherical structure, whereas Brucella sp. (J2) formed the rhombohedral and some spherical calcite crystals, evidence for strain-specific characteristics. It is the first research to provide information regarding the diversity of bacterial communities associated with tufa deposits and the characterization of calcifying bacteria isolated from Jiuzhaigou National Nature Reserve.